Phosphorus and nitrogen fertilization of a Norway spruce forest-effects on needle concentrations and acid phosphatase activity in the humus layer

Abstract

Increased atmospheric deposition of N might eventually lead to P deficiency. The relation between needle P concentration and acid phosphatase activity in the humus layer was studied during 1990-93 in a Norway spruce stand where the water and N and P supplies had been experimentally manipulated since 1988. Treatments included control (C), yearly application of ammonium sulphate (NS), N-free fertilizer (V), granulated wood ash (A), irrigation (I), drought (D) and water plus nutrients in an "optimum" combination (IF). We found indications of a feed-back mechanism for P, where low concentrations in the needles were associated with increased acid phosphatase activity in the humus layer. Acid phosphatase estimations made during moist soil conditions were much more informative than those made during dry conditions. We further argue that a site-specific "base-line" exists for acid phosphatase activity in the soil, mainly originating from enzymes immobilized in the field, but active in the assay. Increased phosphatase activity, above the base line, was generally found in the A, I and NS treatments, but in some cases also in C. Although P and N concentrations were significantly higher in the IF treatment as compared to the C and the D treatments, the P as fraction of N was 0.10 and thus balanced in all cases. In the A and I treatment P:N was around 0.09, while it was only 0.07 in the NS treatment, mainly due to high N concentrations. The latter treatment thus created an imbalanced situation where P additions most likely would have increased tree growth.

Nitrogen and phosphorus in mire plants: variation during 50 years in relation to supply rate and vegetation type

“…Therefore, since the decay rate in Sphagnum litter increases with its N concentration (Limpens and Berendse 2003), an overall increase in the litter decay rates might be supposed to have taken place at these sites. Fertilization with N has also been shown to increase the activity of extracellular acid phosphatase in various forest soils (Clarholm and Rosengren‐Brinck 1995, Treseder and Vitousek 2001). In the same way addition of extra N to peat soils has been shown to increase both phosphatase activity and extractable P in the treated soil (Williams and Silcock 1997, 2001, Kang and Freeman 1999).…”

Effects of Soil Nutrient Availability on Investment in Acquisition of N and P in Hawaiian Rain Forests

“…1), although few studies have examined that possibility. Clarholm and Rosengren-Brinck (1995) found that N fertilization increased phosphatase activity in soils under a Norway spruce forest, although free-living soil microbes could have contributed to phosphatase production. Numerous studies have reported reductions in extracellular acid phosphatase activity per unit root in response to increased P availability ( Fig.…”

Needle analyses and graphic vector analyses of Norway spruce and Scots pine stands

“…The measured effect on foliar concentrations, however, depends on degree of limitation on needle growth and time span between release of the water stress and the sampling. Clarholm and Rosengren-Brinck (1995), for example, reported about equal foliar concentrations of both N and P in current needles for each of the 3 years 1990 -1992 in Skogaby on the south-west coast of Sweden, even though the trees suffered from a serious drought from about 10 May to 15 July 1992. The reason for this is probably, as already discussed, that the foliar concentration of nutrients in late autumn does not necessarily reflect the levels at the time when the drought occurred.…”